package com.blue.base.common.utils.wechat;

import com.alibaba.fastjson.JSONObject;
import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.AlgorithmParameters;
import java.security.Security;
import java.util.Arrays;

/**
 * 小程序工具
 *
 * @author liulei
 * @version 2.0
 */
public class WeChatUtil {

    /**
     * 小程序解析用户信息/手机号信息
     */
    /*public static void main(String[] args) throws Exception {
        String sessionKey = "O5oErZRe+F+xlPV8nqq8kQ==";
        String iv = "bg414r7HjTRmuE6SQabieQ==";
        String encryptedData = "jK+gGwtcBpQF7swpXQjODRddQhgR7ftrfkwaZsD5c/APjymYKjuCDSrkU/FjbP7dC4V8K0/3jmqpIdpHt1YjCW3ZcbjuxoN64di6BFaGz1ZAUxhjJrxJuz7NVSHmwnosEsT0ixSFaE1OAcNDCVhjbUx6nCNcAJ67oLM6wH6XMTZzY0wtLO/7nWB3pBspGfBD1fKJnPD9+BH5gqACOOHy6w==";
        JSONObject jsonObject = decryptData(sessionKey, encryptedData, iv);
        System.out.println(jsonObject);
    }*/

    /**
     * 解密小程序数据
     */
    public static JSONObject decryptData(String sessionKey, String encryptedData, String iv) throws Exception{
        byte[] dataByte = Base64.decodeBase64(encryptedData);
        // 加密秘钥
        byte[] keyByte = Base64.decodeBase64(sessionKey);
        // 偏移量
        byte[] ivByte = Base64.decodeBase64(iv);
        try {
            // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
            int base = 16;
            if (keyByte.length % base != 0) {
                int groups = keyByte.length / base + (keyByte.length % base != 0 ? 1 : 0);
                byte[] temp = new byte[groups * base];
                Arrays.fill(temp, (byte) 0);
                System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
                keyByte = temp;
            }
            Security.addProvider(new BouncyCastleProvider());
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding","BC");
            SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
            AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");
            parameters.init(new IvParameterSpec(ivByte));
            cipher.init(Cipher.DECRYPT_MODE, spec, parameters);
            byte[] resultByte = cipher.doFinal(dataByte);
            if (null != resultByte && resultByte.length > 0) {
                String result = new String(resultByte, "UTF-8");
                return JSONObject.parseObject(result);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}
